This invention belongs to the field of organic chemistry. In particular, it relates to certain azo dyes useful in ink jet ink compositions.
Inks used in ink jet printing systems typically are comprised of various dyes either dissolved in water or an organic solvent or mixtures thereof. There is a need for inks having higher quality images, printing speed, improved water-fastness and lightfastness.
U.S. Pat. No. 5,198,022 describes certain alkali-soluble azo dyes for waterfast ink compositions.
U.S. Pat. No. 5,667,571 describes certain non-pollutive ink compositions using alcohol or glycol ether as solvent, which can be used as writing ink, (industrial) ink jet printing ink, stamp ink, etc. Certain triazinylamino substituted disazo dyes are described.
U.S. Pat. No. 5,795,970 describes certain disazo dyes useful in ink compositions which claims to provide sharp printing images having high optical density and no bleeding which also result in rapid fixing of the ink, water resistance and light resistance, even when printed on plain paper.
U.S. Pat. No. 5,753,016 describes certain disazo dyes which are useful in ink compositions and claim to offer a combination of a high-quality image with a waterfast printing image.
U.S. Pat. No. 5,453,495 describes certain piperazinyl substituted disazo dyes which are useful in ink jet compositions.
U.S. Pat. No. 5,891,230 describes certain disazo dyes useful in ink jet printing. Further examples of disazo dyes can be found in the following: U.S. Pat. Nos. 5,725,644; 5,480,478; 5,888,286; 5,882,392; 5,843,218; and 5,756,693.
Provided are novel black azo dyes which are useful in ink compositions, especially ink jet ink compositions. The dyes and ink compositions of the present invention exhibit a good balance of optical density, color value, water fastness and light fastness. Especially preferred dyes have the following structural formula: 
wherein:
R2, R4, x and M are as defined herein.
In a first embodiment, the present invention provides a compound of Formula (I): 
wherein:
R1 is xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94CO2M, or xe2x80x94SO3M;
R2 is xe2x80x94H, xe2x80x94CO2M, -lower alkyl, -lower alkoxy, nitro; xe2x80x94CF3, halogen, xe2x80x94NHCO-lower alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, or xe2x80x94(CH2)nxe2x80x94CO2M;
R3 is -lower-alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl;
xe2x80x94NHC(O)O-lower-alkyl; or xe2x80x94NHxe2x80x94COxe2x80x94CO2M;
R4 is -lower-alkyl, -lower alkoxy, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl;
xe2x80x94NHC(O)O-lower-alkyl; or xe2x80x94NHCOCO2M;
R5 is xe2x80x94Nxe2x80x94(R6)(R7), or a group of the formula 
R6 is xe2x80x94H, -lower-alkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -lower-hydroxyalkyl, or -lower-cyanoalkyl;
R7 is xe2x80x94H, -lower-alkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -lower-hydroxyalkyl; or -lower-cyanoalkyl;
R8 is xe2x80x94H, -lower-alkyl, -lower-hydroxyalkyl, or xe2x80x94(CH2)nCO2M;
R9 is xe2x80x94H, -lower-alkyl, -lower-hydroxyalkyl, or xe2x80x94(CH2)nCO2M;
R10 is xe2x80x94H, -lower-alkyl, -lower alkoxy, -lower-hydroxyalkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -halogen;
xe2x80x94NR8R9; xe2x80x94(CH2)nSO3M; or xe2x80x94Oxe2x80x94(CH2)mCO2M;
m is 1,2,or 3;
n is 1,2, or 3;
M is xe2x80x94H, xe2x80x94Li, Na, xe2x80x94K, or xe2x80x94Nxe2x80x94(R11)4;
R11 is xe2x80x94H, -lower alkyl, or xe2x80x94(CH2xe2x80x94CH(R12)xe2x80x94O)pxe2x80x94H;
p is 1 to 4;
x is 1 or 2;
R12 is xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH3, or xe2x80x94CH2xe2x80x94OH; and
R13 is xe2x80x94H, lower alkyl, lower alkoxy, halogen, xe2x80x94CO2M, or xe2x80x94SO3M.
In a further preferred embodiment, there is provided a compound of Formula (II): 
wherein:
R2 is xe2x80x94H, -lower-alkyl, -lower-alkoxy, xe2x80x94CO2M, xe2x80x94CF3, xe2x80x94NO2, -halogen, xe2x80x94NHCO-lower-alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, or xe2x80x94(CH2)nxe2x80x94CO2M;
R3 is -lower-alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl,
xe2x80x94NHC(O)O-Iower-alkyl, or xe2x80x94NHCOCO2M;
R4 is -lower-alkyl, -lower alkoxy, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl, xe2x80x94NHC(O)O-lower-alkyl, or xe2x80x94NHCOCO2M;
m is 1,2, or 3;
n is 1,2, or 3;
M is xe2x80x94H, xe2x80x94Li, Na, xe2x80x94K, or xe2x80x94Nxe2x80x94(R11)4;
R11 is xe2x80x94H, -lower alkyl, or xe2x80x94(CH2xe2x80x94CH(R12)xe2x80x94O)pxe2x80x94H;
p is 1 to 4;
x is 1 or 2; and
R12 is xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH3, or xe2x80x94CH2xe2x80x94OH.
In a further preferred embodiment, there is provided a compound of Formula (II): 
wherein:
R2, R4, x, and M are as defined above. In an especially preferred embodiment, R2 is H and R4 is methoxy.
In the above formulae, it is further preferred that R2 is xe2x80x94H, and that R5, R6, and R7 are each xe2x80x94H. Further examples of preferred compounds include the following: 
wherein M is xe2x80x94Nxe2x80x94(R11)4 and R11 is xe2x80x94H, or lower alkyl, optionally substituted by hydroxy. Especially preferred groups M include xe2x80x94NH4, xe2x80x94N(CH3)4, xe2x80x94N(CH2CH3)4, and xe2x80x94NH(CH2CH2OH)3 
In an especially preferred embodiment, there is provided a compound having the formula: 
The compounds of the present invention are usefull as dyes, especially as dyes in ink jet ink compositions. Thus, as a further aspect of the invention, there is provided an ink composition comprising:
(a) at least 0.1% by weight of a compound of Formula I: 
xe2x80x83wherein:
R1 is xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94CO2M, or xe2x80x94SO3M;
R2 is xe2x80x94H, xe2x80x94CO2M, -lower alkyl, -lower alkoxy, nitro; xe2x80x94CF3, halogen, xe2x80x94NHCO-lower alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, or xe2x80x94(CH2)nxe2x80x94CO2M;
R3 is -lower-alkyl, xe2x80x94Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl;
xe2x80x94NHC(O)O-lower-alkyl; or xe2x80x94NHxe2x80x94COxe2x80x94CO2M;
R4 is -lower-alkyl, -lower alkoxy, Oxe2x80x94(CH2)mxe2x80x94CO2M, xe2x80x94(CH2)nxe2x80x94CO2M, xe2x80x94NHCO-lower-alkyl;
xe2x80x94NHC(O)O-lower-alkyl or xe2x80x94NHCO2M;
R5 is xe2x80x94Nxe2x80x94(R6)(R7), or a group of the formula 
R6 is xe2x80x94H, -lower-alkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -lower-hydroxyalkyl, or -lower-cyanoalkyl;
R7 is xe2x80x94H, -lower-alkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -lower-hydroxyalkyl; or -lower-cyanoalkyl;
R8 is xe2x80x94H, lower-alkyl, -lower-hydroxyalkyl, xe2x80x94(CH2)nCO2M;
R9 is xe2x80x94H, -lower-alkyl, -lower-hydroxyalkyl, xe2x80x94(CH2)nCO2M;
R10 is xe2x80x94H, -lower-alkyl, -lower alkoxy, -lower-hydroxyalkyl, xe2x80x94(CH2)nxe2x80x94CO2M, -halogen;
xe2x80x94NR8R9; xe2x80x94(CH2)nSO3M; or xe2x80x94Oxe2x80x94(CH2)mCO2M;
m is 1,2, or 3;
n is 1,2, or 3;
M is xe2x80x94H, xe2x80x94Li, Na, xe2x80x94K, or xe2x80x94Nxe2x80x94(R11)4;
R11 is xe2x80x94H, -lower alkyl, or xe2x80x94(CH2xe2x80x94CH(R12)xe2x80x94O)pxe2x80x94H;
p is 1 to 4;
x is 1 or 2;
R12 is xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH3, or xe2x80x94CH2xe2x80x94OH; and
R13 is xe2x80x94H, lower alkyl, lower alkoxy, halogen, xe2x80x94CO2M, or xe2x80x94SO3M;
(b) water, and
(c) at least one cosolvent.
The dyes of the present invention, when formulated into inks for drop-on-demand jet printing, exhibit all of the necessary properties for producing waterfast printed characters: (1) they become water-insoluble at acidic pH; (2) they produce intense black characters at 2% and above dye concentration in the ink; (3) they are stable in aqueous ink formulations; and (4) they do not clog the small printhead orifices during non-use, thus providing good printhead maintenance when used for drop-on-demand printing. Preferred inks have at least about 0.5% by weight of the dye and at least by 3, preferably 5-25% by weight of cosolvent.
In the above formula, the term xe2x80x9clower alkylxe2x80x9d preferably refers to a straight or branched-chain C1-C4 alkyl group. Examples include methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, isobutyl.
The term xe2x80x9clower alkoxyxe2x80x9d preferably refers to a C1-C4 alkoxy group. Examples include methoxy, ethoxy, propoxy, butoxy and the like.
Likewise, the terms xe2x80x9clower hydroxyalkylxe2x80x9d and xe2x80x9clower cyanoalkylxe2x80x9d preferably refer to C1-C4 alkyl groups substituted by at least one hydroxy or cyano group, respectively.
The term xe2x80x9clower alkylenexe2x80x9d preferably refers to a divalent group of the formula xe2x80x94(CH2)xe2x80x94m wherein m is an integer of from 1 to 4. Examples include methylene, ethylene, propylene, and butylene.
Examples of especially preferred compounds of Formula (I) include the following wherein R1, R2, R3, R4, R5, and M are set forth in the following table:
The compounds of this invention may be prepared by diazotizing an optionally and appropriately substituted aminobenzoic acid, an aminobenzenesulfonic acid, or an aminophthalic acid, coupling with an appropriately substituted aminophenoxyacetic, propionic or butyric acid or an appropriately substituted aminophenylacetic, 2-propionic or butyric acid, rediazotizing the resultant aminoazo intermediate compound, then coupling with an optionally substituted 6-amino-4-hydroxynaphthalene-2-sulfonic acid. If 6-amino-4-hydroxynaphthalene-2-sulfonic acid itself is employed, the disazo intermediate compound may be rediazotized and further coupled with, for example, an optionally substituted coupleable aromatic amine such as, for example, phenyldiethanolamine or dialkylaniline to produce the trisazo dye of Formula I as set forth above.
Examples of aminobenzoic or aninophthalic acids from which ring (A) (as annotated above) may be derived include: 2-, 3-, or 4-aminobenzoic acid, 3-, or 4-aminophthalic acid, 4- or 5-aminoisophthalic acid, 2-aminoterephthalic acid, 2-amino-5-bromobenzoic acid, 2-amino-3-, 4-, or 5-chlorobenzoic acid, 3-amino-4-chlorobenzoic acid, 4-amino-2-chlorobenzoic acid, 5-amino-2-chlorobenzoic acid, 4-amino-5-chloro-2-methoxybenzoic acid, 2-amino-4- or 5-fluorobenzoic acid, 2-amino-5-iodobenzoic acid, 2-amino-3-methoxybenzoic acid, 3-amino-4-methoxybenzoic acid, 4-amino-3-methoxybenzoic acid, 2-amino-3-, 5-, or 6-methylbenzoic acid, 3-amino-2- or 4-methylbenzoic acid, 4-amino-3-methylbenzoic acid, 2-amino-4 - or 5-nitrobenzoic acid, 4-amino-3-nitrobenzoic acid, 2-n-butoxy-4-aminobenzoic acid. Also aminobenzenesulfonic acids from which ring A can be derived include metanilic acid, sulfanilic acid, 4- or 6-chlorometanilic acid, anthranilic acid, sulfanilic acid, a toluidinesulfonic acid, or an anisidinesulfonic acid.
Suitable precursors to ring (B) include, for example, 2xe2x80x2-amino-4xe2x80x2-methoxy-phenoxyacetic acid, 2xe2x80x2-amino-4xe2x80x2-methylphenoxyacetic acid, 2xe2x80x2-amino-4xe2x80x2-methoxy-phenoxypropionic acid, 2xe2x80x2-amino-4xe2x80x2-methylphenoxypropionic acid, 2xe2x80x2-amino-4xe2x80x2-acetamidophenoxyacetic acid; 2xe2x80x2-amino-4xe2x80x2-propoxy-phenoxyacetic acid, 2xe2x80x2-amino-4xe2x80x2-butoxy-phenoxyacetic acid.
Examples of couplers which provide ring (C) include, for example, gamma acid, N-methyl-gamma acid, N-butyl-gamma acid, N,N-dimethyl-gamma acid, N-carboxymethyl-gamma acid, N,N-di(carboxymethyl)-gamma acid, Nxe2x80x94(2-carboxyethyl)-gamma acid, and N,N-diethyl-gamma acid.
Suitable precursors for ring (D), i.e., 
as the R5 substituent include, for example, phenyldiethanolamine, m-tolyl-diethanolamine, 2xe2x80x2,5xe2x80x2-dimethoxyphenyl-diethanolamine, N-phenylglycine, N-phenyl-3-aminopropionic acid, N,N-bis-(2-carboxyethyl)-m-toluidine, 2xe2x80x2-chloro-phenyl-diethanolamine, N,N-bis-(carboxymethyl)-aniline, anthranilic acid, and m-phenylenediamine sulfonic acid.
The compounds of this invention may be isolated readily from aqueous solution as the free acid at pH values below 5. They are quite soluble at alkaline pH in various salt forms including the alkali metal salts (lithium, sodium, potassium) and, especially, as the ammonium, alkanolamine and lower alkyl amine salts. The acid form is readily converted to any of the alkali metal, ammonium, or aliphatic or alkanolamine salts by simply adjusting the pH of an aqueous slurry of the free acid with the appropriate amine, alkali hydroxide or alkali carbonate. Residual undesired salts may be removed from the alkaline dye solutions by means of reverse osmosis.
The compounds of this invention, when applied as the ammonium or substituted ammonium salts by usual ink-jet printing methods, produce water-fast prints on paper because of their decreased water solubility at the lower pH values present on the surface of the paper, especially after removal of solvents and volatile amine by drying.
The dyes of the present invention are thus preferably present in a concentration of about 0.5 to 5 weight % in the ink jet composition, more preferably 1-4%. The dyes are dissolved in a water miscible solvent such as a C1-C4 alcohol, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, s-butanol, t-butanol, or isobutanol; an amide such as N,N-dimethylfornanide or dimethylacetamide; a ketone or ketone alcohol such as acetone or diacetone alcohol; an ether such as tetrohydrofuran or dioxane; an oligo- or poly alkylene glycol such as diethylene glycol, triethylene glycol, poly(ethylene glycol), or poly(propylene glycol) of MW up to about 500; an alkylene glycol or thioglycol such as ethylene glycol, propylene glycol, butylene glycol, 1,5-pentanediol or hexylene glycol; a thiodiglycol; a polyol such as gylcerol or 1,2,6-hexanetriol; a C1-C4 alkyl ether of a C2-C4 alkylene glycol or oligo-C2-C4 alkylene glycol such as 2-methoxyethanol, 2-(2-methoxy-ethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxy)ethoxy]ethanol or 2-[2-butoxy-ethoxy]ethanol; a heterocyclic amide such as 2-pyrrolidone, N-methyl-2-pyrrolidone or a sulfone such as sulpholane; or a mixture thereof.
Preferred water-miscible solvents include 2-pyrrolidone, N-methylpyrrolidone, sulpholane, ethylene glycol, diethylene glycol, triethylene glycol, and 2-methoxy-2-ethoxy-2-ethoxyethanol, 1,2-hexanediol, thiodiethanol, and poly(ethylene glycol) having weight average molecular weights of 200-1000.
The above water-miscible solvents aid in the solubility of the dye in the aqueous ink composition and tend to promote penetration of the dye into the substrate during the printing process. Further examples of such components can be found in U.S. Pat. Nos. 4,963,189; 4,704,113; 4,626,284; 5,891,230; 5,453,495; and 5,198,022, incorporated herein by reference.
The ink compositions may be applied to a substrate in an ink jet printing process. In this process, the ink is formed into small droplets by ejection from a reservoir through a small orifice so that the droplets are directed at a substrate. Such processes are referred to as piezoelectric ink jet printing or thermal ink jet printing. In thermal ink jet printing, programmed pulses of heat are applied to the ink by means of a resistor, adjacent to the onfice during relative movement between the substrate and the reservoir.
Preferred substrates for printing include projector slides; paper, which may have a neutral, acidic or basic character; and textile materials such as cotton, viscose, jute, hemp, flax, nylon and the like.
This invention is fiurther illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated.

The dye depicted above is referred to in the following experiment as Dye #542. This dye is straight-forward to make and results in a dye suitable for ink jet printing. In an ink jet formulation it exhibits good color, optical density, light fastness and water fastness properties, good maintenance performance, and uniform drop formation resulting in good print quality.
The preferred formulation is show below.
Comparisons were made against the above formulation by substituting alternate colorants for Dye 542. The Pro-Jet(copyright) Fast Black 2 dye is the only colorant of the ones evaluated that came close to Dye 542. The dyes evaluated against Dye 542 include:
Inks were made with each of the six colorants and tested on a Lexmark Execjet II. The properties evaluated include idling maintenance, continuous print performance, and uncapped start up after 24 and 72 hours. On several different papers the optical density, color values, water fastness and light fastness properties were compared.
Idling maintenancexe2x80x94The printhead is idled for 30, 60, 90, 120, and 180 seconds and after each time period all of the nozzles are fired. The print sample is then scored by the number of missing or misdirected nozzles at each time and then totaled. The higher the number the worse the performance.
Continuous print performancexe2x80x94The printhead is fired for 1 million, then 2 million, and then 3 million fires. The print sample is then scored by the number of missing or misdirected nozzles after each test and then totaled. The higher the number the worse the performance.
Start upxe2x80x94The printhead remains undisturbed and uncapped for 24 hours and then again for 72 hours. After each time the head is tested to see how m any nozzles are firing at the top and bottom of the print sample. A score of 56xe2x80x9456 is perfect indicating that all 56 nozzles are firing at the top and bottom of the page.
Optical density (OD)xe2x80x94The optical density is measured on a solid block of print over six different plain papers and then averaged. The higher the number the better the OD.
Water fastness (WF)xe2x80x94An image is printed and allowed to dry for three hours. It is then soaked for 5 minutes in DI water. The delta (i.e., change) in optical density is reported before and after soaking the image. This was averaged on two different papers. The smaller the value the better the WF.
Light fastness (LF) The AE (ie., change) is reported before and after exposing an image to a Xenon lamp for 72 hours. This was averaged over three different papers including photo and coated papers. The smaller the value the better the LF.
The table below summarizes the results of the Dye 542 against alternate black dyes which are commercially available and registered worldwide.
After the table the remaining discussion is related to dye synthesis.